Sealing apparatus and method

ABSTRACT

A sealing apparatus ( 10 ) for use in establishing a seal in an annulus ( 12 ) between a mandrel ( 14 ) and a bore wall ( 16 ) has an annular seal element ( 18 ) which extends to sealingly engage the bore wall ( 16 ) and a back-up assembly ( 30 ) for supporting the seal element ( 18 ) and preventing or resisting extrusion of the seal element ( 18 ). The back-up assembly ( 30 ) includes a collar ( 54 ) interposed between a support member ( 40 ) of the back-up assembly ( 30 ) and the end ( 32 ) of the seal element ( 18 ) and which defines a sea-engaging surface ( 60 ), the collar ( 54 ) in use preventing or mitigating damage to the support member ( 40 ) from the seal element ( 18 ).

FIELD OF THE INVENTION

This invention relates to a sealing apparatus and method for use in establishing a seal in an annulus between a mandrel and a bore wall, and to a back-up assembly for use in such apparatus and methods. More particularly, but not exclusively, embodiments of the invention may take the form of a downhole packer for use in sealing a wellbore annulus or bore-lining tubular bore annulus.

BACKGROUND TO THE INVENTION

Sealing apparatus and methods are used in many industries where it is desired to isolate, seal off or otherwise control movement of fluid in a given environment. In the oil and gas industry for example, sealing devices known as packers are commonly used to seal the annulus between a tubing string, such as a production conduit or the like, and a surrounding casing or other tubular.

In some instances, one or more packer may be used to prevent undesired movement of fluid up or down the annulus in order to seal off the wellbore. In other instances, a number of packers may be used to create an isolated annular region which, amongst other things, permits isolation of a problematic formation or permits controlled production from, or access into, a selected region of the formation.

Known packers may comprise an elastomeric annular sealing element mounted on a mandrel and which is capable of being extended radially outwardly to engage, for example, the wall of a bore in which the packer is located, thus providing a seal in the annulus defined between the mandrel and the bore wall. The seal element may be axially compressed, for example by a setting tool, to effect radial expansion.

While such packers are effective and may be used reliably in a number of applications, the high temperature and pressure differences experienced in a downhole environment place particularly high demands on the seal elements of the packer to maintain the seal with the bore wall, the successful maintenance of the seal often being of critical importance to the safe, reliable and economic operation of the wellbore. In some instances, the pressure difference acting across the seal elements may be sufficient to cause extrusion of the seal element, thereby reducing seal performance or making activation more difficult or in more extreme cases risking failure of the seal.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a sealing apparatus for use in establishing a seal in an annulus between a mandrel and a bore wall, the apparatus comprising:

a seal element for providing sealing engagement with a bore wall; and

a back-up assembly comprising:

-   -   a ring member;     -   a support member arranged to extend over at least an end of the         seal element; and     -   a collar having a seal-engaging surface arranged to engage the         end of the seal element, the collar interposed between the end         of the seal element and the support member.

Embodiments of the present invention may, for example, provide support for the seal element in maintaining sealing engagement with the bore wall; prevent or resist extrusion of the seal element; and/or prevent damage to the support member which may otherwise result in reduced performance, control or failure of the seal.

The apparatus may be configurable to define a first, retracted, configuration and a second, expanded, configuration. In use, the apparatus may be run into the bore in the first configuration and activated or otherwise moved from the first configuration to the second configuration to urge the seal element into sealing engagement with the bore wall.

The collar may be configured to assist in supporting the end of the seal element, and in particular to support the end of the seal element when the apparatus is moved from the first configuration to the second configuration during activation and operation of the apparatus. Beneficially, the collar may prevent the seal element from coming into hard contact with the support member and so prevent damage to the support member from the seal element. For example, in applications where the seal element is subject to significant temperature and pressure differentials, embodiments of the present invention resist the transfer of axial forces resulting from the temperature or pressure differentials being transmitted through the seal element to the support member which may otherwise damage or inhibit the ability of the support member to perform its required function of supporting the seal element. In applications where the seal element is required to expand to a large extent, embodiments of the present invention may resist the transfer of the axial forces generated by any axial expansion of the seal element from being transmitted to the support member. Alternatively, or additionally, the collar may assist in preventing or mitigating extrusion of the seal element along the inside of the support member and/or past the ring member, which may otherwise result in reduced performance, control or failure of the seal.

The collar may be of any suitable form and construction.

The collar may be annular and may extend around, or at least partially around, the mandrel.

The collar may be mounted on, or secured to, the mandrel. The collar may be mounted or secured to the mandrel by any suitable means. For example, the collar may be mounted or secured to the mandrel by at least one of a bonded connection, thread connection, interference connection or snap-fit connection.

The collar may be mounted on or secured to the ring member. The collar may be mounted or secured to the ring member by any suitable means. For example, the collar may be mounted or secured to the ring member by at least one of a bonded connection, thread connection, interference connection or snap-fit connection.

The collar may be mounted on or secured to the seal element. The collar may be mounted or secured to the seal element by any suitable means. For example, the collar may be mounted or secured to the seal element by at least one of a bonded connection, thread connection, interference connection or snap-fit connection.

The collar may comprise a first portion defining a first outer diameter and a second portion defining a second outer diameter. The second outer diameter may be greater than the first outer diameter. The collar may define a continuous outer surface between the first and second portions. For example, the collar may comprise a curved outer surface between the first and second portions. Alternatively, the collar may define a stepped profile between the first and second portions. The collar may thus define a distinct radially extending second portion.

The collar may further comprise a third portion defining a third outer diameter, which may be of the same or different outer diameter to the first or second portions.

The collar may be constructed from any suitable material. In particular embodiments, the collar may be constructed from at least one of: a plastic material; a metallic material or alloy; a composite material; and a ceramic material. In particular embodiments, the collar may be constructed from PTFE.

The collar may be configured or arranged to seal against the mandrel. In particular embodiments, the collar may comprise a recess for receiving a seal element, such as an o-ring, although any other suitable seal element may be used as appropriate.

The collar may be configured to engage the support member. In particular embodiments, the collar may be configured to retain the support member.

The collar may be configured to provide a seal between the collar and the support member and/or between the collar and the ring member.

The seal-engaging surface may be provided on an end surface of the collar.

The seal-engaging surface may be offset from an end face of the ring member.

The seal-engaging surface may be provided on an axially directed surface of the collar.

The seal-engaging surface may be provided on the second portion.

The seal-engaging surface may be provided an axially directed surface of the second portion.

The support member may be configured to provide support for the seal element and assist the seal element in maintaining sealing engagement with the bore wall. The support member may be configured to prevent or resist extrusion of the seal element into the annulus between the apparatus and the surrounding bore wall.

The support member may be of any suitable form and construction.

The support member may be mounted on or secured to the collar. The support member may be mounted or secured to the collar by any suitable means. For example, the support member may be mounted or secured to the collar by at least one of a bonded connection, thread connection, interference connection or snap-fit connection.

The support member may be mounted on or secured to the ring member. The support member may be mounted or secured to the ring member by any suitable means. For example, the support member may be mounted or secured to the ring member by at least one of a bonded connection, thread connection, interference connection or snap-fit connection.

The support member may be mounted on or secured to the seal element. The support member may be mounted or secured to the seal element by any suitable means. For example, the support member may be mounted or secured to the seal element at least one of a bonded connection, thread connection, interference connection or snap-fit connection.

At least part of the support member may be interposed between the collar and the ring member.

In the first configuration, the maximum diameter defined by the support member may be less than or equal to the maximum diameter defined by the ring member.

The support member may comprise a single component. For example, the support member may comprise a first back-up element. In particular embodiments, however, the support member may comprise a plurality of components and the support member may comprise the first back-up element and a second back-up element. In some embodiments, the support member may comprise a plurality of each of the first and second back-up elements.

The apparatus may be configured so that the second back-up element is provided between the sealing element and the first back-up element.

In use, the first back-up element and the second back-up element may be configured to be moved under the action of the sealing element from the first, run-in, configuration to the second, set, configuration.

The first back-up element may comprise a slotted portion. In particular embodiments, the first back-up element may define discrete petals, which may be formed between the slots. Beneficially, the provision of slots and petals permits the back-up element to expand to radially greater distances than a non-slotted element and permits the material to expand without elongation. Furthermore, a back-up element comprising slots and petals may expand more easily than a continuous element, resulting in lower stress levels in the sealing element.

The second back-up element may be configured or arranged to cover and/or deform into the gaps between the petals of the first back-up element, in particular on expansion of the first back-up element. In use, the second back-up element can remove any clearances between the first and second back-up elements and any curvature mismatches between the first back-up element and the bore wall. Removal of these clearances and mismatches is important, since the properties of some sealing elements, for example rubber elements, are poor at high temperatures, i.e. around 200° C. At this temperature, rubber is capable of extrusion through any clearances in the back-up elements or between the apparatus and the bore wall.

The first and second back-up elements second back-up element may be of any suitable form and construction.

The first back-up element may be annular. The second back-up element may be annular. In particular embodiments, both of the first and second back-up elements are annular.

In particular embodiments, the second back-up element may be of thinner construction may facilitate the expansion of the back-up system as the sealing element moves from the first, run-in, configuration to the second, set, configuration. This may be of particular benefit in applications and environments where the apparatus is required to seal across a relatively large annular gap. A thinner construction back-up element may also be more compliant and may result in a reduced level of stress being built up in the sealing element during deployment, which stress may otherwise have a detrimental effect on the mechanical properties of the seal element.

The first back-up element may comprise a non-slotted portion.

The first back-up element may at least partially comprise a deformable and/or ductile material.

In use, the first back-up element, in the run-in configuration, may be adapted to engage the bore wall. This permits the first back-up element, in use, to be pinned to the wellbore surface by friction once the sealing apparatus is set. This method of constraint removes any shear loading applied to the first back-up element, which in turn allows for a thinner section to be used. A thinner section reduces the stress imparted into the sealing element as the sealing element moves into the set configuration, and once fully deployed.

The provision of relatively thin construction first and/or second back-up elements reduces the radial extent of the support member and of the apparatus during deployment/run-in into the bore, thereby reducing the risk that the apparatus will be damaged during deployment.

The first back-up element may comprise or define a bore engaging surface. In particular embodiments, more than 50% of the bore engaging surface is, in use, engaged with the bore surface in the set configuration. Such an arrangement ensures that the axial load applied to the sealing element, in use, is not sufficient to overcome the radial load maintaining the sealing apparatus in contact with the bore wall. More than 50% of the slotted portion surface may be engaged with the bore surface in the set configuration. The bore engaging surface may be of relatively high frictional co-efficient. For example, the bore-engaging surface may comprise at least one of a material, profile or coating of high friction co-efficient.

The second back-up element may comprise a ductile material. Providing a ductile element, which can form and adapt in shape, may assist in minimising or at least reducing the stress imparted to the seal element during setting of the apparatus and, when used with a slotted first back-up element, may assist in directing the second back-up element into the between adjacent first back-up element petals. In particular embodiments, the ductile material may comprise stainless steel, although other suitable material may be used where appropriate.

The first back-up element may comprise an upper edge. The upper edge may be chamfered. In particular embodiments, the upper edge may be chamfered towards the bore wall. Beneficially, the provision of a chamfered edge may easily deform into close engagement with the bore wall, thereby reducing the possibility of clearances between the first back-up element and the bore wall opening up.

In embodiments where the first back-up element defines discrete petals, each petal may comprise side edges which lie in a direction parallel to the longitudinal axis of the sealing apparatus. The side edges may be chamfered. In particular embodiments, the side edges may be chamfered towards the bore wall.

The second back-up element may comprise an upper edge. The second back-up element upper edge may be chamfered. In particular embodiments, the second back-up element upper edge may extend above the first back-up element upper edge. In alternative embodiments, the first back-up element upper edge may extend above the at least one second back-up element upper edge. Beneficially, since the side edges may be less exposed than the upper edge, it may be possible to make the edge of the side edge chamfers sharper as they are not as exposed as the upper edge. A sharp edge may form a tighter fit with the second back-up element, thereby minimising the possibility of clearances between the first back-up element and the bore wall opening up.

The second back-up element may comprise a slotted portion. The provision of a slotted second back-up element may also provide for additional expansion. The second back-up element may comprise fewer slots than the first back-up element.

The second back-up element may comprise a sealing element engaging surface.

The sealing element engaging surface may comprise a low friction coating. A low friction coating reduces the stresses imparted into the element material during deployment and under pressure.

At least one of the first and second back-up elements may deform under the action of the sealing element. In some embodiments, the back-up elements may plastically deform. Plastic deformation may reduce the stresses imparted to the sealing element by the back-up elements once the sealing apparatus is set. In other embodiments, the back-up elements may elastically deform. Elastic deformation may allow the back-up elements to at least partially recover to the run-in configuration when it is desired to retrieve the sealing apparatus.

In some embodiments, a first back-up element upper portion may be bent inwards towards a sealing apparatus longitudinal axis. Having the upper portion of the first back-up element facing radially inwards, biases the first back-up element to a run in configuration such that the first back-up element at least partially recovers to the run-in configuration when it is desired to retrieve the sealing apparatus. Such an arrangement may be most effective in an apparatus in which the first back-up element upper edge extends above the at least one second back-up element upper edges.

In some embodiments, the first back-up element may comprises spring steel. Spring steel can be used to assist in returning the sealing apparatus to the run-in configuration when it is desired to recover the sealing apparatus from the bore.

At least one of the back-up elements may be of substantially constant cross-sections. The use of a constant cross-section material, particularly for the first back-up element, may assist in reducing stress concentrations in the first back-up element and may enable a relatively thin section to be used. A thin section will bend more easily and will reduce the stress imparted into the sealing element.

A lower portion of the first back-up element may be received within the ring member.

The ring member may be attached to the non-slotted portion of the first back-up element.

An interface between the slotted and non-slotted portions of the first back-up element may be received within the ring member.

The ring member may be connected to an external surface of the first back-up element lower portion.

The second back-up element may be connected to the ring member.

The ring member may be of any suitable form and construction.

In use, the ring member may beneficially withstand hoop stress imparted to the back-up elements by the differential pressure held by the sealing element.

In particular embodiments, the ring member may define a profiled surface.

The ring member may comprise a profiled outer surface. In use, as the sealing apparatus moves from the first configuration to the second configuration, the first back-up element may bend around at least a portion of the profiled surface. At least a portion of the first back-up element, in the first configuration, may be displaced from the ring member profiled surface. In particular embodiments, the ring member profiled surface may taper axially away from the first back-up element in the first configuration.

The apparatus may comprise a single back-up assembly. In some embodiments, the apparatus may comprise two back-up assemblies. For example, the apparatus may comprise a back-up assembly at both of the respective ends of the seal element.

The seal element may be of any suitable form or construction.

The seal element may comprise an elastomeric seal element.

The seal element may comprise a compression seal element.

The sealing element may comprise a packing element, a cup, an expandable element, a swellable element, an inflatable element or any suitable style of element.

The seal element may be configured to expand in the presence of an activation medium. For example, the seal element may be configured to expand in the presence of oil. Alternatively, the seal element may be configured to expand in the presence of water.

The seal element may comprise a unitary component.

In some embodiments, the seal element may comprise a plurality of components.

In particular embodiments, the seal element may comprise a first seal member and a second member. The first and second seal members may be of different construction. For example, the second seal member may comprise a material of greater hardness than the first seal member. Beneficially, the provision of a second seal member having greater hardness provides an anti-extrusion effect.

The second seal member may be provided between the first seal member and the support member.

The seal element, and in particular embodiments the second seal member of the seal element, may comprise a recess to permit relative movement with the support member.

The seal element may be configured for activation by any suitable means. The seal element may be configured to support a two or multi-stage activation.

The apparatus may be configured to provide an initial engagement with the bore wall. Following the initial activation, the apparatus may be configured to permit pressurised fluid between the seal element and the mandrel which acts to urge or inflate the end of the seal element and the support member.

The apparatus may be configured or arranged for location on the mandrel. In particular embodiments, the apparatus may be mounted or otherwise secured to the mandrel. In particular embodiments, the apparatus may comprise end rings for use in securing the apparatus to the mandrel.

According to a further aspect of the present invention, there is provided a method comprising:

locating a sealing apparatus according to the first aspect in a bore;

activating the apparatus from a first configuration to a second expanded configuration to engage the bore wall.

The method may further comprise de-activating the apparatus.

In some embodiments, the method may further comprise retrieving the apparatus from the bore.

According to a further aspect of the present invention, there is provided a back-up assembly for use with a sealing apparatus used to establish a seal in an annulus between a mandrel and a bore wall, the back-up assembly comprising:

-   -   a ring member;     -   a support member arranged to extend over at least an end of a         seal element of the sealing apparatus; and     -   a collar having a seal-engaging surface arranged to engage the         end of the seal element, the collar interposable between the end         of the seal element and the support member.

According to a further aspect of the present invention, there is provided an assembly comprising a plurality of the apparatus according to the first aspect of the invention.

It should be understood that the features defined above in accordance with any aspect of the present invention or below in relation to any specific embodiment of the invention may be utilised, either alone or in combination, with any other defined feature, in any other aspect or embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a sealing apparatus according to an embodiment of the present invention;

FIG. 2 is an enlarged perspective view of part of the apparatus of FIG. 1;

FIG. 3 is a diagrammatic longitudinal section view of the apparatus shown in FIGS. 1 and 2;

FIG. 4 is a cut-away view of part of the apparatus shown in FIGS. 1, 2 and 3;

FIG. 5 is a longitudinal section view of an apparatus according to another embodiment of the present invention;

FIG. 6 is an enlarged view of part of the apparatus shown in FIG. 5;

FIG. 7 is a longitudinal section view of an apparatus according to another embodiment of the present invention;

FIG. 8 is an enlarged view of part of the apparatus shown in FIG. 7;

FIG. 9 is an end view of an apparatus according to another embodiment of the present invention;

FIG. 10 is a longitudinal section view of section A-A of FIG. 9; and

FIG. 11 is an enlarged view of part of the apparatus shown in FIGS. 9 and 10.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring first to FIG. 1, there is shown a perspective view of a sealing apparatus 10 according to an embodiment of the present invention. In use, the apparatus 10 establishes a seal in an annulus 12 between a mandrel 14 and a bore wall, such as a wellbore or bore-lining tubular bore wall (shown diagrammatically by at 16).

The apparatus 10 is provided on the mandrel 14, the mandrel forming part of a tubing string such as a drill string, production conduit or the like (not shown).

In use, the apparatus 10 is run into the bore wall 16 on the mandrel 14 in a first, retracted, configuration before being activated to a second, expanded, configuration in which the apparatus 10 sealing engages the bore wall 16.

The apparatus 10 includes an annular seal element 18 mounted on the mandrel 14 and, in use, it is the seal element 18 which expands to sealingly engage the bore wall 16.

In the embodiment shown in FIG. 1, the seal element 18 is bonded to the mandrel 14. However, it will be recognised that the seal element 18—or indeed any other component of the apparatus 10—may alternatively be a slip on component and the apparatus 10 may be located over a tubular string component, such as a drill string, completion string or the like.

Referring now also to FIG. 2, which shows an enlarged perspective view of part of the apparatus 10 with the mandrel removed for clarity, annular gauge rings 20, 22 are provided at respective ends of the apparatus 10. As shown most clearly in FIG. 2, the gauge rings 20, 22 having radially extending holes defining bores 24 for receiving grub screws (not shown). The bores 24 are provided in an annular portion 26 of the gauge rings 20, 22 which also have a tapered portion 28 at their distal ends.

As shown in FIG. 2, and referring also to FIGS. 3 and 4 which show a diagrammatic longitudinal section view and a cut-away view of part of the apparatus 10, a back-up assembly 30 for supporting an end 32 of the seal element 18 is provided at one end of the apparatus 10. In the embodiment shown in FIGS. 1 to 4, a single back-up assembly 30 is provided. However, it will be recognised that in other embodiments (such as will be described with reference to FIGS. 5, 6, 7 and 8), back-up assemblies may be provided at both ends of the seal element 18.

The back-up assembly 30 is provided around the mandrel 14 and between the gauge ring 20 and around the end 32 of the seal element 18. In use, the back-up assembly 30 amongst other things supports the expanding seal element 18 in maintaining sealing engagement with the bore wall 16 and prevents or resists extrusion of the seal element 18 which may otherwise reduce performance or risk failure of the seal.

The back-up assembly 30 comprises an annular ring member 34 mounted on the mandrel 14. A seal recess or groove 36 is provided on an inner surface 38 of the ring member 34, the seal groove 36 receiving a seal element in the form of a o-ring (not shown), although other seal elements may be used where appropriate. In use, the o-ring prevents fluid leakage between the ring member 34 and the mandrel 14.

The back-up assembly 30 further comprises a support member 40 which supports the end 32 of the seal element 18. During expansion of the seal element 18, the support member 40 supports the expanding seal element 18 in maintaining sealing engagement with the bore wall 16 and prevents or resists extrusion of the seal element 18 into the annulus 12.

In the embodiment shown in FIGS. 1 to 4, the support member 40 is formed from two elements or layers, a first back-up element 42 and a second back-up element 44. The first back-up element 42 has an annular portion 46 and a slotted portion defining a number of petals 48. The petals 48 extend over the end 32 of the seal element 18 and bend or pivot radially outwards towards the bore 16 as the seal element 18 expands. The second back-up element 44 is provided within the first back-up element 42 and between the first back-up element 42 and the seal element 18 and has an annular portion 50 and a slotted portion defining a number of petals 52. In use, the second back-up element 44 is formed and arranged to cover, deform into, or otherwise fill the gaps created between the petals 48 of the first back-up element 42 as they extend.

The annular portions 46, 50 of the support member 40 are provided between the ring member and the mandrel 14 and may be used to secure the support member to the other parts of the apparatus 10.

Interposed between the support member 40 and the end 32 of the seal element 18, an annular insert or collar 54 is positioned on the mandrel 14. In the embodiment shown in FIGS. 1 to 4, the collar 54 comprises a first diameter portion 56, a second diameter portion 58 having a diameter greater than the first diameter portion 56 and a seal-engaging surface 60. The collar 54 defines a curved tapering outer surface between the first diameter portion and the second diameter portion. In use, the collar 54 prevents damage to the support member 40 from seal element 18, in particular from axial forces transmitted through or generated in the seal element 18 during use and which may otherwise result in reduced performance, control or failure of the seal.

As shown in FIG. 4, the seal element 18 in this embodiment comprises a first inner seal member 62 and a second outer seal member 64. The seal members 62, 64 may be formed separately and bonded or moulded together to define the seal element 18 of the apparatus 10. The second outer seal member 64 beneficially is constructed from a material of greater hardness than the first seal member 62 and, in use, provides an anti-extrusion effect at a selected region or regions of the seal element, in particular at the end region 32 of the seal element.

Referring now to FIGS. 5 and 6, there is shown an apparatus 110 according to another embodiment of the present invention, FIG. 5 showing a longitudinal section view and FIG. 6 showing an enlarged view of part of the apparatus 110. The apparatus 110 is similar to the apparatus 10 shown and described with reference to FIGS. 1 to 4 and, for brevity and ease of reference, like components of the apparatus are represented by like numerals incremented by 100.

In this embodiment, the apparatus 110 comprises two back-up assemblies 130 located at ends 132 of a seal element 118 and, in use, the apparatus 110 is activated by compression, whereby relative movement of the back-up assemblies 130 towards each other (or of one assembly 130 moving closer to the other) results in axial compression and radial expansion of the seal element 118 into sealing engagement with the bore.

As shown most clearly in FIG. 6, the annular collar 154 of this embodiment comprises a first diameter portion 156 and a second diameter portion 158 and a seal-engaging surface 160. However, in this embodiment the first diameter portion 156 does not extend axially beyond the end face of ring member 120. Also, the collar 154 defines a distinct radial step between the first diameter portion 156 and the second diameter portion 158.

In the illustrated embodiment, the seal element 118 comprises a single seal member 162. However, it will be recognised that the seal element 118 may also comprise a second seal member similar or identical to the seal element 18 described above.

Referring now to FIGS. 7 and 8, there is shown an apparatus 210 according to another embodiment of the present invention, FIG. 7 showing a longitudinal section view and FIG. 8 showing an enlarged view of part of the apparatus 210. The apparatus 210 is similar to the apparatus previously described and, for brevity and ease of reference, like components of the apparatus are represented by like numerals incremented by 200.

In this embodiment, the apparatus 210 comprises two back-up assemblies 230 located at ends 232 of a seal element 218 and, in use, like the apparatus 110 the apparatus 210 is activated by compression, whereby relative movement of the back-up assemblies 230 towards each other (or of one assembly 230 moving closer to the other) results in axial compression and radial expansion of the seal element 218 into sealing engagement with the bore.

As shown most clearly in FIG. 6, the annular collar 254 of this embodiment comprises a first diameter portion 256 and a second diameter portion 258 and a seal-engaging surface 260. Like the embodiment of FIGS. 1 to 4, in this embodiment the collar 254 defines a curved tapering outer surface between the first diameter portion 256 and the second diameter portion 258. In this embodiment, however, in addition to being axially interposed between the end 232 of the seal element 218 and the support member 240, the collar 254 is also radially interposed between the support member 240 and the mandrel 214 and, in use, the collar 254 may be utilised to retain the support member 240.

As in the embodiment shown and described with reference to FIGS. 5 and 6, in this embodiment the seal element 218 comprises a single seal member 262. However, it will again be recognised that the seal element 218 may also comprise a second seal member similar or identical to the seal element 18 described above. The illustrated seal element 118 further comprises internal and external grooves.

Referring now to FIGS. 9, 10 and 11, there is shown an apparatus 310 according to another embodiment of the present invention, FIG. 9 showing an end view, FIG. 10 showing a longitudinal section view along A-A, and FIG. 11 showing an enlarged view of part of the apparatus 310. The apparatus 310 is similar to the apparatus previously described and, for brevity and ease of reference, like components of the apparatus are represented by like numerals incremented by 300.

In this embodiment, the apparatus 310 comprises a single back-up assembly 330 located at an end 332 of seal element 318 and, in use, the apparatus 310 is activated to define a cup seal with the bore.

Referring in particular to FIG. 11, in this embodiment the annular collar 354 comprises a first diameter portion 356 and a second diameter portion 358 and a seal-engaging surface 360. In this embodiment, the first diameter portion 356 extends axially towards and into a recess in the inner surface of in a similar manner to the collars 54, 254. In common with the collar 154, the collar 354 also defines a distinct radial step between the first diameter portion 356 and the second diameter portion 358.

In this embodiment, in addition to being axially interposed between the end 332 of the seal element 318 and the support member 340 and radially interposed between the support member 340 and the mandrel 314, the collar 354 is also radially interposed between the seal element 318 and the mandrel and is bonded, moulded or otherwise secured to the seal element 318. To facilitate this further interpositioning, the collar 354 comprises a third diameter portion. In the illustrated embodiment, the third diameter portion has a greater diameter than the first diameter portion 356 and a smaller diameter than the second diameter portion 358.

Referring again to all of FIGS. 9, 10 and 11, the seal element 318 comprises a second seal member (as shown most clearly in FIG. 11) and a third seal member positioned adjacent to seal member. As described above, the seal members may be of different or similar construction and made from different or similar materials, as required.

As described above, this embodiment differs from those shown and described in FIGS. 5 to 8 in that the apparatus 310 defines a cup seal with the bore.

As can be seen in FIGS. 9 and 10, gauge ring 322 comprises bores which permit fluid passage between the inner surface of the seal element 318 and the mandrel 314. In use, following initial activation of the apparatus 310 fluid may be directed through the bores and between the inner surface of the seal element 318 and the mandrel, thereby providing an additional inflation force to assisting in setting and maintenance of the seal.

It should be understood that the embodiment described herein is merely exemplary and that various modifications may be made thereto without departing from the scope of the invention.

For example, the apparatus may further comprise an intermediate layer between the first back-up element and the/each second back-up element. The intermediate layer may extend above and below the first back-up element upper edge. The intermediate layer may comprise a strong flexible material, and in particular embodiments the intermediate layer may comprise a woven steel mesh. Using a flexible intermediate layer such as a woven steel mesh further minimises the existence of gaps between the first and second back-up elements in the second, expanded, configuration. The flexible material fills gaps which may exist between the first and second back-up elements. The intermediate layer may be thinner than either or both of the first and second back-up elements and, in some embodiments, the intermediate layer may be wrapped over an upper edge of the second back-up element. In alternative embodiments, the intermediate layer may be wrapped over the upper edge of the first back up element. 

1. A sealing apparatus for use in establishing a seal in an annulus between a mandrel and a bore wall, the apparatus comprising: a seal element for providing sealing engagement with a bore wall; and a back-up assembly comprising: a ring member; a support member arranged to extend over at least an end of the seal element; and a collar having a seal-engaging surface arranged to engage the end of the seal element, the collar interposed between the end of the seal element and the support member.
 2. The apparatus of claim 1, wherein at least one of: the apparatus is configurable to define a first, retracted, configuration and a second, expanded, configuration; the collar is configured to assist in supporting the end of the seal element; the collar is configured to support the end of the seal element when the apparatus is moved from the first configuration to the second configuration.
 3. (canceled)
 4. (canceled)
 5. The apparatus of any preceding claim, wherein the collar is annular.
 6. The apparatus of claim 1, wherein at least one of: the collar is mounted on, or secured to, the mandrel; the collar is mounted on, or secured to, the mandrel by at least one of a bonded connection, thread connection, interference connection or snap-fit connection.
 7. (canceled)
 8. The apparatus of claim 1, wherein at least one of: the collar is mounted on, or secured to, the ring member; wherein the collar is mounted on, or secured to, the ring member by at least one of a bonded connection, thread connection, interference connection or snap-fit connection.
 9. (canceled)
 10. The apparatus of claim 1, wherein at least one of: the collar is mounted on, or secured to, the seal element; the collar is mounted on, or secured to, the seal element by at least one of a bonded connection, thread connection, interference connection or snap-fit connection.
 11. (canceled)
 12. The apparatus of claim 1, wherein at least one of: the collar comprises a first portion defining a first outer diameter and a second portion defining a second outer diameter; the second outer diameter portion is of greater diameter than the first outer diameter portion; the collar defines a continuous outer surface between the first and second portions; the collar comprises a curved outer surface between the first and second portions; the collar defines a stepped profile between the first and second portions.
 13. (canceled)
 14. (canceled)
 15. (canceled)
 16. (canceled)
 17. The apparatus of claim 12, wherein one of: the collar further comprises a third portion defining a third outer diameter; the collar further comprises a third portion defining a third outer diameter and the third portion is of the same outer diameter as the first or second portions; the collar further comprises a third portion defining a third outer diameter and the third portion is of a different diameter to the first and/or second portions.
 18. (canceled)
 19. (canceled)
 20. The apparatus of claim 1, wherein at least one of: the collar is constructed from at least one of: a plastic material; a metallic material or alloy; a composite material; and a ceramic material; the collar is constructed from PTFE.
 21. (canceled)
 22. The apparatus of claim 1, wherein at least one of: the collar is configured or arranged to seal against the mandrel; the collar is configured to provide a seal between the collar and the support member; the collar is configured to provide a seal between the collar and the ring member.
 23. The apparatus of claim 1, wherein the collar comprises a recess for receiving a seal element.
 24. The apparatus of claim 1, wherein at least one of: the collar is configured to engage the support member; the collar is configured to retain the support member.
 25. (canceled)
 26. (canceled)
 27. (canceled)
 28. The apparatus of claim 1, wherein at least one of: the seal-engaging surface is provided on an end surface of the collar; the seal-engaging surface is offset from an end face of the ring member; the seal-engaging surface is provided on an axially directed surface of the collar; the collar comprises a first portion defining a first outer diameter and a second portion defining a second outer diameter and the seal-engaging surface is provided on the second portion; the collar comprises a first portion defining a first outer diameter and a second portion defining a second outer diameter and the seal-engaging surface is provided on an axially directed surface of the second portion.
 29. (canceled)
 30. (canceled)
 31. (canceled)
 32. (canceled)
 33. The apparatus of claim 1, wherein at least one of: the support member is mounted on, or secured to, the collar; the support member is mounted on, or secured to, the collar by at least one of a bonded connection, thread connection, interference connection or snap-fit connection.
 34. (canceled)
 35. The apparatus of claim 1, wherein at least one of: the support member is mounted on, or secured to, the ring member; the support member is mounted on, or secured to, the ring member by at least one of a bonded connection, thread connection, interference connection or snap-fit connection; at least part of the support member is interposed between the collar and the ring member; in the first configuration the maximum diameter defined by the support member is less than or equal to the maximum diameter defined by the ring member.
 36. (canceled)
 37. The apparatus of any preceding claim, wherein at least one of: the support member is mounted on, or secured to, the seal element; the support member is mounted on, or secured to, the seal element at least one of a bonded connection, thread connection, interference connection or snap-fit connection.
 38. (canceled)
 39. (canceled)
 40. (canceled)
 41. The apparatus of claim 1, wherein the support member comprises a first back-up element.
 42. (canceled)
 43. The apparatus of claim 41, wherein at least one of: the support member comprises a plurality of first back up elements; the first back-up element comprises a slotted portion; the first back-up element defines discrete petals; the first back-up element is annular; the first back-up element comprises a non-slotted portion; the first back-up element at least partially comprises a deformable and/or ductile material; the first back-up element is configured to engage the bore wall; the first back-up element comprises or defines a bore engaging surface; the first back-up element deforms under the action of the sealing element; the first back-up element comprises spring steel; a lower portion of the first back-up element is received within the ring member.
 44. The apparatus of claim 42, wherein at least one of: the support member comprises the first back-up element and a second back-up element; the apparatus is configured so that the second back-up element is provided between the sealing element and the first back-up element; the second back-up element is configured or arranged to cover and/or deform into the gaps between the petals of the first back-up element; the second back-up element is annular; the second back-up element is of thinner construction than the first back-up element; the second back-up element comprises a ductile material; the ductile material comprises stainless steel; the second back-up element comprises a slotted portion; the second back-up element comprises a sealing element engaging surface; the second back-up element deforms under the action of the sealing element, the deformation being elastic or plastic; the second back-up element is connected to the ring member.
 45. (canceled)
 46. (canceled)
 47. (canceled)
 48. (canceled)
 49. (canceled)
 50. (canceled)
 51. (canceled)
 52. (canceled)
 53. (canceled)
 54. (canceled)
 55. (canceled)
 56. (canceled)
 57. (canceled)
 58. (canceled)
 59. (canceled)
 60. (canceled)
 61. (canceled)
 62. (canceled)
 63. (canceled)
 64. (canceled)
 65. (canceled)
 66. The apparatus of claim 1, wherein at least one of: the ring member defines a profiled surface; the ring member defines a profiled outer surface.
 67. (canceled)
 68. The apparatus of claim 1, wherein one of: the apparatus comprises a single back-up assembly; the apparatus comprises two back-up assemblies.
 69. (canceled)
 70. The apparatus of claim 1, wherein the seal element comprises at least one of: an elastomeric seal element; a compression seal element; a packing element; a cup; an expandable element; a swellable element; and an inflatable element.
 71. The apparatus of claim 1, wherein at least one of: the seal element is configured to expand in the presence of an activation medium; the seal element is configured to expand in the presence of oil; the seal element is configured to expand in the presence of water.
 72. (canceled)
 73. (canceled)
 74. The apparatus of claim 1, wherein the seal element comprises a unitary component.
 75. The apparatus of claim 1, wherein at least one of: the seal element comprises a plurality of components; the seal element comprises a first seal member and a second member; the seal element comprises a first seal member and a second member and the first and second seal members are of different construction; the seal element comprises a first seal member and a second member and the second seal member comprises a material of greater hardness than the first seal member; the seal element comprises a first seal member and a second member and the second seal member is provided between the first seal member and the support member.
 76. (canceled)
 77. (canceled)
 78. (canceled)
 79. (canceled)
 80. The apparatus of claim 1, wherein the seal element comprises a recess configured to permit relative movement with the support member.
 81. The apparatus of claim 1, wherein at least one: the apparatus is configured or arranged for location on the mandrel; the apparatus is mounted on the mandrel; the apparatus comprises end rings for use in securing the apparatus to the mandrel.
 82. (canceled)
 83. (canceled)
 84. A method comprising: locating a sealing apparatus according to any preceding claim in a bore; activating the apparatus from a first configuration to a second expanded configuration to engage the bore wall.
 85. The method of claim 84, further comprising at least one of: de-activating the apparatus; and retrieving the apparatus from the bore.
 86. (canceled)
 87. A back-up assembly for use with a sealing apparatus used to establish a seal in an annulus between a mandrel and a bore wall, the back-up assembly comprising: a ring member; a support member arranged to extend over at least an end of a seal element of the sealing apparatus; and a collar having a seal-engaging surface arranged to engage the end of the seal element, the collar interposable between the end of the seal element and the support member.
 88. An assembly comprising a plurality of the apparatus according to claim
 1. 89. (canceled)
 90. (canceled)
 91. (canceled)
 92. (canceled) 